Former Secretary of State John Kerry said President Donald Trump's rhetoric "has stepped over the line," fueling North Korea's angst and causing them to say, "Hey, we need a bomb."

Kerry made the comments in an interview with CNN's Christiane Amanpour.

"I think what the president needs to do is make sure he's not feeding into North Korea's fear of regime change or of a unilateral attack," Kerry told Amanpour. "I think the rhetoric today has frankly stepped over the line in respect to the messages that are being sent.

"It's given North Korea a reason to say, 'Hey, we need a bomb. Cause if we don't have a bomb, we're gonna not be able to protect ourselves and they'll come after us,'" Kerry said.

Kerry was State Department chief from 2013 until 2017.

"We've got to get into the dialogue. It's not gonna be easy, it's not gonna happen overnight. Lots of negotiations have taken a long time," Kerry said.

"It pushes people away, I mean, this childish kind of, the rhetoric," Kerry said. "If name calling was going to solve this problem, Donald Trump would have already solved the problem. So, that's not going to move anybody to do what you have to do."